wasm: fix marshaling of LocalNames and NameMap

Author: 张志强

wasm/section.go

@@ -1189,6 +1189,9 @@ func (s *LocalNames) UnmarshalWASM(r io.Reader) error {
 }
 
 func (s *LocalNames) MarshalWASM(w io.Writer) error {
+	if _, err := leb128.WriteVarUint32(w, uint32(len(s.Funcs))); err != nil {
+		return err
+	}
 	keys := make([]uint32, 0, len(s.Funcs))
 	for k := range s.Funcs {
 		keys = append(keys, k)
@@ -1235,6 +1238,9 @@ func (m NameMap) UnmarshalWASM(r io.Reader) error {
 	return nil
 }
 func (m NameMap) MarshalWASM(w io.Writer) error {
+	if _, err := leb128.WriteVarUint32(w, uint32(len(m))); err != nil {
+		return err
+	}
 	keys := make([]uint32, 0, len(m))
 	for k := range m {
 		keys = append(keys, k)

wasm/section_test.go

@@ -0,0 +1,91 @@
+// Copyright 2020 The go-interpreter Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package wasm_test
+
+import (
+	"bytes"
+	"io/ioutil"
+	"path/filepath"
+	"testing"
+
+	"github.com/go-interpreter/wagon/wasm"
+)
+
+func TestSectionCustom(t *testing.T) {
+	fname := "testdata/custom_funcs_locals.wasm"
+
+	t.Run(filepath.Base(fname), func(t *testing.T) {
+		raw, err := ioutil.ReadFile(fname)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		r := bytes.NewReader(raw)
+		m, err := wasm.DecodeModule(r)
+		if err != nil {
+			t.Fatalf("error reading module %v", err)
+		}
+
+		nameCustom := m.Custom("name")
+		if nameCustom == nil {
+			t.Fatal("can not find name custom section")
+		}
+
+		var nSec wasm.NameSection
+		err = nSec.UnmarshalWASM(bytes.NewReader(nameCustom.Data))
+		if err != nil {
+			t.Fatalf("error name Section Unmarshal %v", err)
+		}
+
+		// check FunctionNames MarshalWASM func
+		if len(nSec.Types[wasm.NameFunction]) == 0 {
+			t.Fatalf("%s doesn't have custom FunctionNames section", fname)
+		}
+
+		sub, err := nSec.Decode(wasm.NameFunction)
+		if err != nil {
+			t.Fatalf("error NameSection Decode NameFunction %v", err)
+		}
+
+		funcNames, ok := sub.(*wasm.FunctionNames)
+		if !ok {
+			t.Fatal("error NameSubsection type")
+		}
+
+		buf := new(bytes.Buffer)
+		err = funcNames.MarshalWASM(buf)
+		if err != nil {
+			t.Fatalf("error FunctionNames Marshal %v", err)
+		}
+		if !bytes.Equal(buf.Bytes(), nSec.Types[wasm.NameFunction]) {
+			t.Fatal("error Marshal and Unmarshal FunctionNames")
+		}
+
+		// check LocalNames MarshalWASM func
+		if len(nSec.Types[wasm.NameLocal]) == 0 {
+			t.Fatalf("%s doesn't have custom LocalNames section", fname)
+		}
+
+		sub, err = nSec.Decode(wasm.NameLocal)
+		if err != nil {
+			t.Fatalf("error NameSection Decode NameFunction %v", err)
+		}
+
+		localNames, ok := sub.(*wasm.LocalNames)
+		if !ok {
+			t.Fatal("error NameSubsection type")
+		}
+
+		buf = new(bytes.Buffer)
+		err = localNames.MarshalWASM(buf)
+		if err != nil {
+			t.Fatalf("error LocalNames Marshal %v", err)
+		}
+		if !bytes.Equal(buf.Bytes(), nSec.Types[wasm.NameLocal]) {
+			t.Fatal("error Marshal and Unmarshal LocalNames")
+		}
+
+	})
+}